1. Field of the Invention
The invention relates to a driver assistance system for motor vehicles and relates in particular to a semiautomatic parking aid for multilane vehicles.
2. Description of Related Art
Parking aids assist a driver of a vehicle in parking his vehicle. In the past, essentially passive parking aids in the form of orientation objects on the motor vehicle or on the parking spot have been predominant, but in recent years active parking aids in particular have taken precedence. As a rule, ultrasonic sensors are installed in the rear bumpers and occasionally also in the front bumpers of the vehicle to measure the distance from such obstacles based on a determination of the transit time of the ultrasonic waves emitted by the sensors and reflected on these obstacles. If the measured distance is less than a predefined value, then a warning signal is output in general, the frequency of repetition of this signal increasing progressively with a further reduction in distance. These so-called active systems reduce the risk of a collision with obstacles or people in the vicinity of the vehicle. However, the driver of the vehicle does not receive any assistance in maneuvering into the parking space or parking spot with these systems.
Driver assistance systems, which measure the size of a potential parking space and take over the steering of the vehicle during parking, have been developed for this purpose. The corresponding parking assistance systems usually operate semiautomatically. They are activated by the driver of the vehicle as needed and they measure the available space by means of ultrasonic sensors as the vehicle drives slowly past the parking space. After the driver has stopped the vehicle, a control unit in the parking assistance system (assuming the parking space is large enough) calculates the ideal parking path from the starting position. Finally, the driver of the vehicle engages the reverse gear and limits his actions to accelerating, clutching and braking while a steering actuator, controlled by the control unit, takes over the steering of the vehicle until the optimum parking position has been reached.